flutter painting on canvas and erase drawing - flutter

Question

i am working on a canvas drawing module in to it i need to erase user drawing
basic funda is
adding image in canvas
user can draw on image using pencil (i.e black color) now user can erase this black color on erase function (i.e clear user drawing )
my try is :
case PaintMode.eraser:
print('eraser**** _image Painter!!!*'); // print(_painter.color)
// canvas.saveLayer(Offset.zero & size, Paint());1
var _painterTemp = _painter!
// ..color = Colors.transparent.withOpacity(0.8)//also tried it
..strokeCap = StrokeCap.round
..blendMode = BlendMode.clear;
for (var i = 0; i < _offset!.length - 1; i++) {
if (_offset[i] != null && _offset[i + 1] != null) {
final _path = Path()
..moveTo(_offset[i]!.dx, _offset[i]!.dy)
..lineTo(_offset[i + 1]!.dx, _offset[i + 1]!.dy);
} else if (_offset[i] != null && _offset[i + 1] == null) {
canvas.drawPoints(PointMode.points, [_offset[i]!], _painterTemp);
}
}
// canvas.restore();//1
break
but i am getting black lines only
took reference from
https://github.com/yellowQ-software/yellowQ-Flutter-Image-Painter
edit-----
i've edited like
case PaintMode.eraser:
print('eraser**** _image Painter!!!*');
var _painterTemp = _painter!
..color = Colors.transparent
..blendMode = BlendMode.clear; //srcOver
for (var i = 0; i < _offset!.length - 1; i++) {
if (_offset[i] != null && _offset[i + 1] != null) {
final _path = Path()
..moveTo(_offset[i]!.dx, _offset[i]!.dy)
..lineTo(_offset[i + 1]!.dx, _offset[i + 1]!.dy);
canvas.drawPath(_path, _painter);
canvas.drawPath(_path, _painterTemp);
canvas.saveLayer(Offset.zero & size, Paint());
} else if (_offset[i] != null && _offset[i + 1] == null) {
canvas.drawPoints(PointMode.points, [_offset[i]!], _painter);
canvas.drawPoints(PointMode.points, [_offset[i]!], _painterTemp);
}
// canvas.saveLayer(Offset.zero & size, Paint()); //1
}
// canvas.restore();//1
break;
but not working but getting custom painter called canvas.save() or canvas.saveLayer() at least 773 more times than it called canvas.restore().
any help?